Topics Covered

Introduction

Nanotechnology is being used more and more in consumer products - over 400 products in the U.S. alone are labeled as ‘nano-based’. The discovery of carbon nanotubes and graphene, and our increasing understanding of the properties of materials on the nanoscale, is leading to an explosion in the commercialization of next generation technologies.

Although the nano boom will bring a wealth of positive changes, it is simultaneously giving rise to a persistent form of pollution which is too small to detect or contain easily. The health effects of nanopollution are yet to be fully understood, making nanopollution yet another man-made environmental impact with uncertain effects in the long term.

Nanopollution does not just come from deliberately created nanomaterials - many industrial processes produce nanowaste which often escapes to the atmosphere untreated. Image credit: Photos.com.

Nanopollution refers to all the waste matter or byproducts that occur during the manufacture or use of nanoscopic devices or material. For example, fullerenes, molecular spheres of carbon, are used in products like industrial lubricants and sports equipment. Some amount of these fullerenes end up in landfills exposed to the open air, the soil, and the water table. Fullerenes, like many other nanomaterials, are non-biodegradable, and it is difficult to determine what effects they may have on the ecosystem.

Effect of Nanoparticles on Human Health

Universities and research centres around the world are carrying out an ever-increasing amount of research on the effects of nanoparticles on humans. Experts have stated that people are already exposed to high levels of nanopollution in urban areas due to the exhaust from cars and manganese oxide from construction sites, and researchers are working hard to determine and classify the toxicity of these pollutants.

Nanoparticles are so small that they can easily penetrate living cells. The human body is designed to detect foreign objects and produce phagocytes to break down the foreign object. However, if the body's phagocytes are constantly digesting nanoparticles, the cells cannot break down bacteria or other debris inside the body.

The potential damage nanoparticles can do has been understood for quite some time - a study conducted by researchers at Johns Hopkins Hospital way back in 1941 discovered that nanoscopic particles, when inhaled, could enter the brain via the olfactory tract, as was seen in their experiment with chimps and rhesus monkeys.

Another study by toxicologist Eva Oberdorster from Southern Methodist University involved exposing captive large-mouth bass to various levels of carbon-60, or buckminsterfullerene. She discovered an immune response in the livers of the fish population two days later. This reveals that the small nanoparticles were able to bypass the fishes' immune systems, thereby raising the concerns that these nanoparticles could cause some damage to the body before they are even detected.

Moreover, scientists at Trinity College Dublin have linked rheumatoid arthritis and the development of autoimmune diseases to exposure to nanoparticles. Nanoparticles in human cells caused the specific transformation of the amino acid arginine into the molecule called citrulline, which has the potential to develop autoimmune conditions such as rheumatoid arthritis.

Although there are numerous unanswered questions, research like this is gradually throwing more light on the hazards of nanopollution, which will help in creating more awareness and hopefully lead to safer workplaces and a cleaner environment.

Measuring Nanomaterials in the Environment

Another key area of ongoing research is in determining the concentration of nanopollutants in a given environment. Nanoparticles are incredibly hard to isolate and quantify becuase of their size, so novel methods are required before we can even fully understand the scale of the issue.

Whilst nanopollution is going to be an important issue in the next few years, nanotechnology also has the potential to help to reduce pollution, through the use of cleaner materials, and through novel environmental remediation techniques. Image credit: Jiang Lab, University of Washington.

Measuring the amount of nanoparticles in any ecosystem is crucial to how it is later dealt with. A new, cost-effective invention gives hopes of measuring carbon nanotube concentration in plants using microwave heating. Carbon nanotubes are found in all carbon-based nanomaterials, and hence needs close monitoring. Microwave heating reveals not just the presence but also the concentration. This method could well become a testing standard for the U.S. Environmental Protection Agency.

Preventing Nanopollution

Although the fight against nanopollution has begun, there is a long way to go. One research showed that not all nanoparticles are toxic, as most of them have a stable protective coating rendering them nontoxic to living cells. What this means is that surface chemistry of nanoparticles play a big role in classifying them as toxic or not.

Most commentators agree that the best way to work towards a solution to the problems posed by nanopollution is initially through increased levels of communication and discussion. Collaboration between experts from a variety of scientific disciplines, such as materials science, toxicology, chemical engineering and environmental sciences is essential for the development of new concepts and technologies to deal with this new environmental threat.

It seems almost certain that strict regulations will be necessary on the nanomaterials which can be released into the environment from manufacturing facilities. Regulators are hesitant to act, however, because of the unclear consensus from the research to date about the health implications of exposure to nanopollution. They are therefore reluctant to place undue limits on a growing industry without concrete evidence - unfortunately this means that, for now, polluters are continuing to release materials with largely unknown health effects into the air, water, and soil.

In the coming years hopefully, we will see nano-based companies competing against each other to implement the most effective new practices to prevent nanopollution.

Reducing Pollution with Nanotechnology

It is not all bad news for nanotechnology and the environment. We are exposed to many kinds of nanoparticles which occur in nature and do not seem to have any negative health effects, so it is likely that many of the new, man-made nanomaterials will be similarly harmless.

Nanotechnology can also help in reducing and treating other kinds of pollution. Recent discoveries suggest that nanotechnology could be as transformative in this field as it has been and will continue to be in many others.

In February 2007, a new type of pollution control technology won the £185,000 Brian Mercer Award for Innovation from the Royal Society. This new technology could greatly decrease the amount of pollution emitted by a number of industrial processes. The technology comprises nano-porous fibres having many fine pores that are less than 1,000th of the width of a human hair and contain materials to trap volatile hydrocarbons and other gases so they can be removed from the air flow.

The technology effectively traps carbon dioxide and other pollutants so that they can be removed and sometimes even recycled back into the production process. The beverage industry would probably benefit the most from this technology. However, it can also be put to use for removing benzene from petrol vapour at filling stations, and many other areas.

According to the application, devices using the technology can be customized to either remove or recycle the gases by just varying the composition of fibres used. The fibres have the potential to be spun with a high surface area to volume ratio, thus providing the devices with higher efficiency and small configurations and hence making them ideal for applications where space is a constraint.

Conclusion

Nanopollution is a growing issue - we are already releasing a large amount of nanomaterials into the environment, and we do not have a strong idea how many of them will impact human health.

Research is progressing rapidly, and hopefully we will build a picture of which materials need particular care and attention, and develop methods of dealing with them, before too much damage is done.

Regulators have been reluctant to place any heavy restrictions on nanopolluters, as that could place a serious block on the growth of industries outside of nanotechnology, as well as the booming nano sector itself. This may be sensible in the short term, but could create issues later on if we cannot develop methods to treat or remediate nanopollution.

Graphene oxide membranes have been receiving attention for their extremely powerful separation abilities and the ease at which it can be modified, allowing for membrane permittivity to be fine-tuned. These membranes show the potential to be used for water purification, ‘green’ gas purification and greenhouse gas capture.